In recent years, electrophotographic apparatuses typified by copiers and laser beam printers have been improved in various performance properties including operation speed and image quality, and it is desired to utilize electrophotographic apparatuses as printers capable of not only copying and outputting documents in offices but also outputting a large volume of high quality images. Therefore, great importance is attached to achieving both high image quality and high durability of electrophotographic apparatuses.
Here, when attention is focused on electrophotographic photosensitive members mounted in electrophotographic apparatuses, it is important that surface layers of the electrophotographic photosensitive members is made to provide charge transporting performance in order to attain high image quality of elecrophotographic apparatuses. For this reason, a charge transporting material is often incorporated into the surface layer of an electrophotographic photosensitive member. However, when a charge transporting material is incorporated into the surface layer of an electrophotographic photosensitive member, the mechanical strength of the surface layer degrades due to the plasticity of the charge transporting material, which may likely to cause a degradation in the running performance of the electrophotographic photosensitive member and the electrophotographic apparatus.
In the light of the above-mentioned circumstances, there have been studied materials for attaining both high charge transporting performance and high mechanical strength to surface layers of electrophotographic photosensitive members. Japanese Patent Application Laid-Open No. 2005-241974 discloses an electrophotographic photosensitive member having a surface layer formed using a resin excellent in mechanical strength. Japanese Patent Application Laid-Open No. H11-237751 discloses an electrophotographic photosensitive member having a surface layer formed by three-dimensionally crosslinking conductive particles and a curable compound. Japanese Patent Application Laid-Open No. 2001-166502 discloses an electrophotographic photosensitive member having a surface layer formed by three-dimensionally crosslinking a curable compound having a structure to provide charge transporting performance.
However, such electrophotographic apparatuses, in which an electrophotographic photosensitive member having the surface layer disclosed in Japanese Patent Application Laid-Open No. 2005-241974, Japanese Patent Application Laid-Open No. H11-237751 or Japanese Patent Application Laid-Open No. 2001-166502 is mounted, still leave room for further improvement from the viewpoint of achieving both high image quality and high durability.